The use of rapid FT-NIR methods to predict soluble solids, pH, titratable acidity and phenols of clingstone peaches (‘Baby Gold 9’)

The aim of this study was to evaluate the ability of FT-NIR technique applied on whole fruits and puree to predict soluble solids (SSC), titratable acidity (TA), pH and total phenolic compounds of clingstone peaches.
Even in the case of puree, the destructive analysis based on FT-NIR reading would be much faster and easy to perform, if compared to the chemical reference method (Folin and Ciocalteu assay). A total of 50 fruits ‘Baby Gold 9’ were harvested and labeled opposite sides.
For each side of the intact fruit 3 spectra were acquired using a multipurpose analyzer (MPA Bruker) spectrometer, working in the range of 4000-12500 cm^-1. Then a wedge from each side was taken corresponding to the region of acquisition, peeled and homogenized; the puree was put in a glass petri dish and a single spectrum was acquired.
On the same puree soluble solids, pH, titratable acidity were determined, while a portion was stored at -80°C until determination of phenol contents of the flesh.
In addition, the skins were stored at -80°C for determination of phenols.
The spectral data were analyzed using the OPUS software (version 7.2, Bruker Optics), for intact clingstone peaches 3 spectra were averaged for each side.
The spectra were subjected to different pre-treatments (vector normalization (VN), multiplicative scatter correction (MSC), first derivate (FD), second derivate (SD), and their combination). As for the analysis on intact clingstone peaches using the SNV transformation for soluble solids content and phenols of the skin good results were obtained with R² in cross validation of 84.9 and 68.1, and RMSECV of 0.435 and 15.7, respectively.
For pH prediction R² of 52.1 and RMSECV of 0.084 were obtained, whereas for acidity and phenols of the flesh R² of 42.7 and 36.8, and RMSECV of 0.101 and 1.161, were found, respectively.
For purees, best results were observed for soluble solids with coefficient of determination of 84.1 and RMSECV of 0.454, while less lower accuracy was found for flesh phenols, followed by acidity and pH, with R² of 52.9, 44.1 and 33.2, respectively.
This study suggested that this type of non-destructive technique can be a valid support to predict internal content of SSC, acidity and skin phenol content, normally evaluated with destructive and time consuming analysis, showing that no improvement was obtained with the homogenization of the sample.
In addition, it encourages further studies on method optimization and extension to other cultivars.

VIII International Postharvest Symposium: Enhancing Supply Chain and Consumer Benefits – Ethical and Technological Issues

M.L. Amodio, F. Piazzolla, F. Colantuono, G. Colelli

spectra, non-destructive measure, puree, skin

https://doi.org/10.17660/ActaHortic.2018.1194.159